Oxidation of c -Type Cytochromes by the Membrane-Bound Cytochrome Oxidase (Cytochrome aa 3 ) of Blue-Green Algae

Abstract

Respiratory particles containing an aaa-type cytochrome oxidase were prepared from Anacystis nidr ans, Synechocystis 6714, Synechococcus livi-dus, Anabaena vaiabilis, Nostoc sp. strain MAC, Nostoc muscorum, and Mastigocldus laminosus. Oxidatdon of c-type cytochromes by membrane preparations of the different blue-green algae was observed using purified cytochromes from horse heart, Candida krusei, tuna, Saccharomyces ovi-formis, Rhodospirilum rubrum, RhodospiAlium molischianum, Rhodopseu-domoias pastris, Rhodocyclus purpureus, Paracoccus denitrificans, Ana-cystis nrdus, Anabaena vaiabilis, Euglena gracilis, and Scenedesmus obliquws. Rapid oxidations were consistently observed with the mitochon-drial c-type cytochromes (horse heart cytochrome c reacts most rapidly) and with cytochromes c2 from Rhodopseudomonaspalustris and Rhodocydlus puwpreus, in contrast, the cytochrome c2 from Rhodospirillum rubrmn and the plastidic cytochromes from E. gracilis and Scenedesmus obliquus were inactive with all membrane preparations. AU reactions were inhibited by low concentrations of KCN, NaN3, and CO, and they were activated by Tween 80, thus indicating participation of the terminal oxidase. The results are discussed in view of the spectral similarities between the terminal oxidase of blue-green algae and the mitochondrial aa3-type cytochrome oxidase of plants and other eukaryotes.